Laminates are layered materials consisting of several layers of material webs impregnated with duroplastic or thermoplastic resins, which are stacked upon each other in the desired sequence and are extruded together. Fiber or tissue webs are used as material webs. For impregnation by duroplastic resins, melamine-, urea-, phenolic-, epoxy-resins or the like are, for instance, utilized. While duroplastic resins cure or harden through the application of heat or by a chemical reaction, thermoplastic resins cure by cooling.
An example of such layered materials is decorative laminates, which are used for surface coating of chipboard. These decorative laminates consist of a core and surface layer, which is again composed of melamine or phenolic resin impregnated papers. The surface layer resting upon the core layer is herein provided with a decorative printing, for instance, with imitation wood graining.
Continuous processes are increasingly used for fabrication of laminates, since these provide an increased quantity as well as quality compared with discontinuous processes. A continuously working apparatus for fabrication of decorative laminates is known from DE-OS 32 47 146. The apparatus shown there consists of a double band press, upstream of which several take off units are arranged. Storage coils are located in the take off units, from which the resin impregnated material webs are taken off and are combined or stacked into a layered formation. This layered formation enters into a double band press and is extruded there into a laminate web with the application of area pressure and possibly heat. The double band press is followed downstream by a cooling arrangement utilizing a water spray, where the laminate web is cooled. Subsequently, the back side of the laminate web is roughened downstream in a grinding station in order to assure an improved glueability or adhesion of the decorative laminate upon a carrier plate. A laminate web treated in such a way is then wound in a reel-up arrangement upon a storage coil or is subdivided into panels or plates in a transverse cutting station. The grinding station can herein be equipped with diamond tipped round brushes.
It is disadvantageous in this known apparatus that, especially with high production and also higher feed velocities of the laminate webs, there occurs too high generation of heat at the ground surface, which leads to unsightly surfaces having poor mechanical properties. In case of sensitive laminates, this can even lead to increased waste. An additional disadvantage is that the grinding brushes are very quickly loaded with grinding dust from the laminate surface, so that these grinding brushes must be replaced relatively often. The laminate fabrication must, however, be interrupted when this is done, so that these frequent down times lead overall to a reduction of the output of the continuously working installation. Apart from this, increased expense for maintenance is involved.